21425 has 6 divisors (see below), whose sum is σ = 26598. Its totient is φ = 17120.

The previous prime is 21419. The next prime is 21433. The reversal of 21425 is 52412.

21425 = 103² + 104².

21425 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

21425 is an esthetic number in base 9, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in 3 ways, for example, as 5041 + 16384 = 71^2 + 128^2 .

It is not a de Polignac number, because 21425 - 2⁸ = 21169 is a prime.

It is an Ulam number.

It is a Duffinian number.

21425 is strictly pandigital in base 6.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21425.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 404 + ... + 453.

It is an arithmetic number, because the mean of its divisors is an integer number (4433).

2²¹⁴²⁵ is an apocalyptic number.

21425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21425 is the 104-th centered square number.

It is an amenable number.

21425 is a deficient number, since it is larger than the sum of its proper divisors (5173).

21425 is an equidigital number, since it uses as much as digits as its factorization.

21425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 867 (or 862 counting only the distinct ones).

The product of its digits is 80, while the sum is 14.

The square root of 21425 is about 146.3728116830. The cubic root of 21425 is about 27.7741180364.

Adding to 21425 its reverse (52412), we get a palindrome (73837).

It can be divided in two parts, 2 and 1425, that multiplied together give a triangular number (2850 = T₇₅).

The spelling of 21425 in words is "twenty-one thousand, four hundred twenty-five".